Researchers have found a drug that appears to be very effective in preventing the re-occurrence of a common type of breast cancer. This drug, herceptin, was so effective, that clinical trials were stopped early to inform the participants of the results.

Four years ago, Adriana Jenkins was diagnosed with breast cancer. She says, "My cancer was extremely aggressive, and I wanted to do everything I could possibly could, to make sure it didn't come back."

Following surgery to remove the tumor, Adriana received chemotherapy and herceptin, a drug that is given intravenously. Herceptin is normally used to treat breast cancer patients after their cancer has returned.

But in Adriana's case, she took the drug to prevent the cancer from coming back. Researchers used the same approach in treating other breast cancer patients.

In clinical trials, women reported that after four years, cancer returned in 15 percent of those who received chemotherapy and herceptin, compared to 33 percent of those who got only chemotherapy.

Doctor Eric Weiner of the Dana-Farber Cancer Institute explains how herceptin works. He says, "This drug robs the cancer of a growth factor that is a chemical that drives the cancer to grow."

Although herceptin fights breast cancer, some women have experienced side effects such as a weakened heart. But despite that, doctors say the benefits are so strong, they are encouraging many women to add herceptin to their cancer treatments